Comprehensive shape control technology for CSP hot strip mills

Abstract

Abstract:With the increasing demand on higher strip quality, the profile and flatness of hot rolling strips have become subjects of concern, particularly for compact strip product (CSP) hot strip mills. Based on the roll contour, control model, and rolling process, a comprehensive shape control technology is proposed and applied to CSP hot strip mill of Lianyuan steel, which includes optimization and design of the work roll contour and varying contact back-up roll (VCR) plus backup roll contour, analysis of the flatness feedback control model, as well as improvement of the rolling process control system. The application of the technology has significantly improved the shape control performance. The roll wear is improved and the general roll consumption of the finishing mill is reduced by 29.86%. The percentages that satisfy the control target ranges of the average strip flatness and crown are increased by approximately 15.40% and 14.82%, respectively. The rejection rate of grade Q235 due to shape quality problem is reduced monthly by 39.69%, which creates significant economic benefits for the plant.

Research and application of approximate rectangular section control technology in hot strip mills

“…For example, He et al [8] proposed a set of control methods for the shape of hot-rolled high-strength magnetic yoke steel, including the process of roughing and finishing and the roll contour technology. Chen et al [9] proposed a strip contour control method applicable to compact strip plant production line. In order to produce high-precision strip steel, Zhao et al [10] proposed a shape control model for hot strip rolling.…”

Analysis of rate dependency on roll force calculation during hot strip rolling based on Karman equation

“…Stick/slip friction criterion is judged by resistance stress to prevent the friction stress from exceeding resistance stress. An industrial application is made on the last stand of a CSPÒ hot finishing rolling mill, 20 as shown in Figure 1. It consists of seven-stand four-high rolling mill, and the strip is non-oriented silicon steel.…”

A New Mill Design for the Production of a Strip with Zero Strip Crown

“…To control the strip profile and flatness, various technologies have been developed in recent decades. As shown in Figure , they may be categorized as follows: 1) Multi‐high mill such as a six‐high mill, cluster mill, or Z‐mill; 2) roll crown control such as pair cross mill (PCM); 3) roll bending control such as a work roll bender and backup roll bender; 4) roll shifting control such as continuously variable crown (CVC) or work roll shifting; and 5) multiple control methods such as a six‐high CVC mill and other combinations of the above methods …”

“…As shown in Figure 1, they may be categorized as follows: [1,2] 1) Multi-high mill such as a six-high mill, cluster mill, or Z-mill [3][4][5][6] ; 2) roll crown control such as pair cross mill (PCM) [7][8][9] ; 3) roll bending control such as a work roll bender and backup roll bender [10] ; 4) roll shifting control such as continuously variable crown (CVC) or work roll shifting [11][12][13] ; and 5) multiple control methods such as a six-high CVC mill and other combinations of the above methods. [14][15][16][17][18][19] A question that may be raised is, "Is it possible to produce a strip with flat strip profile, which means a perfectly rectangular cross section, so as to achieve zero strip crown or zero edge drop, and at the same time, to eliminate the flatness problem once and for all?" Unfortunately, this is very difficult to achieve with conventional mills, even with a sound strategy for mill setup and control.…”